The overall objective of this project is the elucidation of the biochemical mechanisms involved in the hormonal control of lipolysis and cyclic AMP accumulation in adipocytes in response to training by endurance running. The major objectives are to determine the functional capacity of the beta-adrenergic receptor and its coupling to adenylate cyclase in intact fat cells and isolated membranes. Emphasis will be placed on regulation of lipolysis by cyclic AMP in adipose tissue from trained rats. Cyclic AMP metabolism will be studied directly as will enzyme activities that are involved in its production and metabolism. Subcellular distribution of these enzymes and their sensitivity to various inhibitors will be assessed. Emphasis is also placed on the hormone-sensitive lipase as activated by cyclic AMP dependent protein kinase or by other mechanisms. Differences in catecholamine sensitivity in fat cells from untrained and trained rats that have been treated in vitro with other hormones known to be altered during exercise and training will also be studied.